I have a late 2009 i7 iMac that spends most of its time reading and swapping files from the 2TB hard drive, even though it’s only 40% full.

I want to buy an affordable (240GB/£160) Firewire external SSD, and install Yosemite on to it, then use that as my startup disc.

Will I get an appreciable jump in speed, or will I be limited by Firewire 800 speeds ?

Has any one tried this ?


As you know with SATA connection you get 3 to 6 Gb/s.

With Firewire you get < 1 Gb/s data transfer.

To be specific:

Firewire 800 is 800 Mbits/s (Mb/s) not 800 Mbytes/s (MB/s) [8 bits in a byte] its a common misconception. so Firewire 800 is rated up to 80 MB/s.

  • Buscar is correct, however you might see an improvement in some operations depending on how much data is going across the firewire bus. It's a good way to test the setup and get a good working boot drive configured. But why not then swap the SSD into the Mac? – Steve Chambers Nov 19 '14 at 21:43
  • Thanks Buscar and Steve. Steve: I don’t want to replace my internal HD, just keep my 830GB of info on it. I wanted to use the (relatively small) external SSD as the system startup disc. This would also avoid the cost of prising open my Mac and replacing the current HD. – user101295 Nov 20 '14 at 19:37
  • It is possible that will work for you, since the OS X on the external disk will issue just a commands to the CPU and RAM to do stuff which is mainly located on the build in disk. Thus the amount of data flow from the external disk (the OS X) would not be so large. The SATA connection is for the build in disk to allow the huge amounts from RAM to Disk and back. So it might be worth a try. – Ruskes Nov 20 '14 at 19:45

iMac that spends most of its time reading and swapping files from the 2TB hard drive

That sounds like a problem that needs to be addressed.

1) how do you know this is what is happening?

2) How much memory does your computer have?

3) if you are Terminal-fluent, provide the results of ls -l /var/vm

  • 1) I don’t. But sometimes my HD spends long periods of writing/reading when no applications are open (I can hear it, and see evidence on Activity monitor). 2) 8GB. 3)total 2097152 drwxr-xr-x 3 root wheel 102 20 Nov 17:28 . drwxr-xr-x 28 root wheel 952 18 Oct 08:52 .. -rw------- 1 root wheel 1073741824 20 Nov 17:28 swapfile0 ~ 4 $ – user101295 Nov 20 '14 at 19:41

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